As a conventional ultrasound diagnostic system, a wagon-type system provided with a movable wagon on which various equipment is mounted is the mainstream. Currently, however, a portable ultrasound system superior in portability is coming into a market. By way of example, a portable ultrasound system referred to as a notebook type is provided with a structure allowing a cover-like case incorporating a display device to be folded onto a thin main body unit (Patent Document 1, Patent Document 2, etc.) A portable ultrasound system referred to as a vertical type, is provided with a display device on the front surface of a main body unit being small in thickness, and a foldable keyboard is provided on the surface of the main body unit below the display device. With this configuration, in the state of using, input operation is performed by extending the keyboard in front of the display device, whereas in the state of nonuse, the keyboard is folded in such a manner as covering the display device. It is also suggested that the display device of this vertical type system is provided with a tilt mechanism so as to enhance visibility of the display device, and this allows the vertical angle to be changeable (Patent Document 3).